Containers for food or other articles thermoformed from plastic material normally comprise a lid and base that may be hinged to each other or may be separate parts. In order to hold the lid and base of the container in closed condition, it is necessary that the lid and base have a locking structure that can be manually opened and closed with relative ease. However, the structure should be capable of locking the container in closed condition to avoid accidental opening.
Various types of locking structures have been proposed in the past. For example, cylindrical male and female locking elements have been proposed as disclosed in British Patent Specification 2,118,142. Elongated rib structures comprising cooperating male and female elements have been proposed as disclosed in Canadian Patent 1,117,491 and U.S. Pat. No. 5,046,659. In the prior elongated rib structure locking elements, the locking action has taken place on the long sides or the ends of the ribs. This requires that the ribs be located in such a position on the container that both sides or ends of the ribs are engageable by the cooperating male and female elements to provide the locking action.
It would be desirable to provide a locking structure with male and female locking elements where the elements contain hook structures that interlock with respect to each other when the container is in a closed condition. This would improve the strength of the locking structure and allow hand closure of it while still holding significant weight.
The primary object of the present invention is to provide a locking structure for a container that provides a tighter lock between the container lid and base.
Another object of the invention is to provide a locking structure for a container that is easy to operate in opening and closing the locking structure on the container.